Exemplary embodiments of an apparatus and method for equalizing hot fluid exit plane plate temperatures relate to plate-type fluid-to-fluid heat exchangers. More specifically, the embodiments relate to heat exchangers constructed to minimize deleterious effects attributable to cold spots on plates that form a heat exchanger matrix.
A fluid-to-fluid heat exchanger matrix is designed to extract energy from, for example, hot exhaust gas. As the hot gas stream proceeds through the matrix, a cooler opposing gas stream draws thermal energy from the hot gas stream across intervening plates and cools the hot gas stream. Accordingly, toward the end of the hot gas flow path, i.e. the hot gas exit plane, the temperature of the hot gas is low as it comes into contact with a metal surface of a plate that separates incoming cooler gas from the exiting cooled hot gas. At the hot gas exit plane, the plate temperature may be low due to close proximity to the cool gas entry plane. When the hot gas contacts cool or low temperature portions of the metal plate separating the two gas streams, a dew point temperature of hot gas constituents may be reached, and condensation may occur. Thus, when corrosive constituents are present in the gas streams, corrosive condensation or fouling due to particulate accumulation may cause premature failure of the heat exchanger matrix.
An ideal fluid-to-fluid heat exchanger (hereinafter a gas-to-gas heat exchanger by way of example only) should cool hot process gas to a temperature that merely approaches the dew point temperature of corrosive constituents so that the hot gas exits the heat exchanger matrix without first condensing the constituents on a cold spot near the hot gas exit plane, or any portion of a plate of the heat exchanger matrix. Heat exchangers generally do not accommodate true counterflow of hot and cool gas streams and therefore hot process gas, at a plane perpendicular to gas flow, does not cool evenly as it progresses through and exits the heat exchanger matrix. Thus, cold spots may form on plates of the heat exchanger matrix.